I know it may not be the most desireable carb, but it's an original equipment for a 51 (and others). I've recently switched to a dual carb set-up (see below, my unabashed, gratuitous showing off of my last 3 month's labor!).

Anyway, I won't be using this Carter WE anymore, and it is complete and works fine (ran when parked!). Free to good home or consideration for any charitable contributions of parts sent back my way.
http://i151.photobucket.com/albums/s144/vegas_paul/DSC00905.jpg

I would be happy to pay the shipping on the WE if it is still available. I think this would be identical to the one my 52 uses. Right now Old Spot's engine waits for a rebuild. Your engine is beautiful!